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The Goods On Oils


PHaT MR30

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The oil change is approaching and I'm a stuck between two viscosities to choose right now for my RB20.

My car is an 180sx with an unopened RB20DET in it with basic bolt-on : FMIC, 3" downpipe, apex'i 3.5" catback, kinugawa RB25 highflow running 0.9b, custom FFP, 450cc injectors, standard S13 airbox with STD filter in it, tuned with nistune and 8200rpm rev limit.

Cooling wise engine is equipped with a 19 row oil cooler and a full copper 32mm thick water radiator with the viscous fan.

RB26 oil pump on STD collar, RB20 water pump.

Still more a road toy than a track toy but the car is more and more track oriented as the time goes.

I was running valvoline synpower 5w30 last year, did a track day where the oil was hitting 120°C after around 8 or 10 laps of a 3.2 km track, the thinning was severe as I saw oil pressure dropping around the 3b anything over 5000rpm up to the rev limit.

On the road the oil was barely hitting 100°C during engine bashing but the pressure remained stable, on normal driving it hit 85/90°C.

I never saw a drop of oil in the OCT even after the track day, it remained empty.

Because of the oil pressure problems I switched to Synpower 5w40 and did an UOA of the 5w30 oil to see if I damaged the bottom end. Tin, lead and copper concentrations where near 0 so the bottom end didn't suffered at all from oil starvation, if there was any, but chromium and iron where sky high compared to the first UOA I did on this engine after road usage only. Given the trashing it went through I didn't paid too much attention. The engine is still starting fine, and there is no wear on the cams or lifters.

With the 5w40 on the road I lost some temperature, I get 80/85°C, 95°C when trashing it.

On an other track day on a different track which is not too different from the first track just a little longer (3.5 km), I couldn't get the oil to 120°C but the air temperature was a little slower than the last one.

The OCT catched around 150 mL of oil during that day. The engine never spilled a drop of oil before on the road with this viscosity or the 5w30 even on the track. But with the 5w40 I got 150 mL of oil for 260 km of track driving. Pressure wise it was fine, between 4b and the oil pump by pass pressure around 6b from 3500 rpm and up.

I will make an other UOA to see if internal wise there is a gain to switch from the 5w30 to the 5w40 but I'm not sure on which viscosity I should get for hot weather/track condition.

Winter is coming in europe so the 5w30 is the way to go, but next year when I'll get back on track I'm leaning toward 5w30 viscosity but with better thermal caracteristics or a lighter 5w40.

For information the viscosities of the 5w30 :

11.9mm²/s at 100°C

68mm²/s at 40°C

Viscosity index : 171

The 5w40 ones :

13.9mm²/s at 100°C

85mm²/s at 40°C

Viscosity index : 169

Any advice or specific oil that could suits the engine needs ?

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For track use if you are seeing temps that high consistently I would be going a 10w60 eg the castrol fully synth. 5w30 is way too thin for a track car especially if you are doing track laps in the summer months.

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120°C is my limit, once I hit this temperature I do a lap cooldown and I exit the track for a while.

New trackday today with the same 5w40 oil that did the previous trackday. The oil as thinned out quite a bit during the day, but it had around 4000 km and one trackday already. The morning was wet so I could'nt go all out on the engine until late morning. The pressure were on par with the previous trackday and temperature were between 90/100°C.

On the afternoon the track was finally totally dry and I bashed the engine as much as I could. I didn't see 120°C, the air temprature was cool enough to stay in my comfortable zone. On the longests run (~25min) I barely see 115°C. Tires are the weak point now.

But the pressure were lower and lower as the day passes and didn't go past 4.5b during the last session around the 110°C mark.

The OCT didn't catched anything this time, so my theory as going too thick on viscosity maybe a problem with the oil flooding of the head.

It seems that I really need a light 40 or heavy 30 wt oil to have sufficient pressure and no oil spilling.

Well it still a recent problem to me, and I only encountered oil spilling once. But it seems that too high viscosity is not good for my engine at least.

Given how the trackday went today I might go for an other run with the 5w40 but maybe an other brand.

10w60 seems way too thick given my experience. The problem with too thick oil is the thicker it is, the less oil is entering the engine.

So the film strength is better but there is less oil to build that wall so all in all I'm not sure that its a good idea, and less oil alos mean less cooling of the bearings and pistons.

I'm an engine bench operator and I have made some test bench of different oil viscosities on one prototype engine. Oil flow entering the engine when going thicker oil reduces dramatically and when at high revs camshaft and crankshaft bearing temperature were a good 30°C higher with the thicker oil meaning that the lubrication was not so good.

In fact it was so bad in terms of bearings temperature that we couldn't do the tests we wanted to do anymore as we hit the max temprature we were allowed.

Because of this I just want to run the thinnest oil that give good pressure on all the rev range when at maximum temperature. 5w40 is meeting this but oil spilling was my concern when running it.

I wonder if castrol is giving viscosities of their oil on their website.

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No I never tested motul oil as its quite expensive here. I could buy twice as many valvoline than motul.

The VI rating is interesting for the 5w40 viscosity, it should be more stable at high temperature than the valvoline and maybe in the long run. :)

But the TBN seems rather low, I don't run ethanol so acidic attacks of the oil is not yet a problem but I'm not too confident. I was already not too confident with the TBN of the valvoline oils which are in the low 10. lol

I've never asked the TBN rating of used oil on the analysis I made so I don't know how my engine "deplete" the oil, maybe I should to know if the 300V is a good alternative or not.

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I spun a big end bearing at Wakefield with valvoline in my car many years back and never used it since. I'v used 300v in all my track bikes under the most abusive conditions and even though it's not a turbo car, the bikes gearbox shares the engines oil aswell allowing me to feel the changes in the viscosity through the gearbox and what I noticed was how stable it is even when belting it in summer 3 track days and 5000ks and feels great. so for me it's a case of if it ain't broke don't fix it.

it's quality shit but pricey

Edited by mr skidz
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120°C is my limit, once I hit this temperature I do a lap cooldown and I exit the track for a while.

New trackday today with the same 5w40 oil that did the previous trackday. The oil as thinned out quite a bit during the day, but it had around 4000 km and one trackday already. The morning was wet so I could'nt go all out on the engine until late morning. The pressure were on par with the previous trackday and temperature were between 90/100°C.

On the afternoon the track was finally totally dry and I bashed the engine as much as I could. I didn't see 120°C, the air temprature was cool enough to stay in my comfortable zone. On the longests run (~25min) I barely see 115°C. Tires are the weak point now.

But the pressure were lower and lower as the day passes and didn't go past 4.5b during the last session around the 110°C mark.

The OCT didn't catched anything this time, so my theory as going too thick on viscosity maybe a problem with the oil flooding of the head.

It seems that I really need a light 40 or heavy 30 wt oil to have sufficient pressure and no oil spilling.

Well it still a recent problem to me, and I only encountered oil spilling once. But it seems that too high viscosity is not good for my engine at least.

Given how the trackday went today I might go for an other run with the 5w40 but maybe an other brand.

10w60 seems way too thick given my experience. The problem with too thick oil is the thicker it is, the less oil is entering the engine.

So the film strength is better but there is less oil to build that wall so all in all I'm not sure that its a good idea, and less oil alos mean less cooling of the bearings and pistons.

I'm an engine bench operator and I have made some test bench of different oil viscosities on one prototype engine. Oil flow entering the engine when going thicker oil reduces dramatically and when at high revs camshaft and crankshaft bearing temperature were a good 30°C higher with the thicker oil meaning that the lubrication was not so good.

In fact it was so bad in terms of bearings temperature that we couldn't do the tests we wanted to do anymore as we hit the max temprature we were allowed.

Because of this I just want to run the thinnest oil that give good pressure on all the rev range when at maximum temperature. 5w40 is meeting this but oil spilling was my concern when running it.

I wonder if castrol is giving viscosities of their oil on their website.

Interesting, so you find the volume of oil drops so much that your temperatures go up. This means that whilst you get the required pressure you end up having other issues. I guess it is always a balancing game.

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10W60 is way too thick. I'd only use that in a lawnmower with flogged out rings.

If your oil is getting too hot, you need an oil cooler. Thick oil flows slower so it gives less cooling to internal components and piston crowns.

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Oil selection depends on tolerances really. 5W30 for some and 10W60 for others. It all depends.

I think your main issue is cooling. Maybe reevaluate your cooler efficiency, especially net airflow.

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10W60 is way too thick. I'd only use that in a lawnmower with flogged out rings.

If your oil is getting too hot, you need an oil cooler. Thick oil flows slower so it gives less cooling to internal components and piston crowns.

A lot of race teams and performance work shops use it. It is only the hot temperature that is thicker, it is still an SAE 10 oil at the colder temperature, if you draw a scale it will only be when it gets hotter that it acts like a thicker oil.

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Yep but still too thick at high temps to my tastes, 60wt is useful when hitting above 130°C as it has the viscosity of a 40wt oil at 100°C give or take.

I think that my cooling system is barely enough to sustain track sessions above 30°C, below that it seems to be OK.

I can't really go bigger than 19 row where the oil cooler is located. But I sure can enlarge the air intake and fabricate ducting to channel the air through the radiator.

@Rolls

It's not the volume in itself but the oil quantity that disminish when going thicker.

So if we go too thick we may change the lubrication mode annihilating any benefit that a better oil film strength could bring. :(

At least that's what I witnessed on the tests I had to do.

@mrskidz

yes the VI is quite impressive over what valvoline propose on their oil. :D
I may give it a go to see how it perform.

I find valvoline oil to be on the weak side in terme of viscosity stability over time/kilometers. It really broke down as time passes and usually in the UOA the oil has gone almost 10 wt thinner in 5000k's. :(

But I don't have results with other brands yet.

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on another note. Have you guys seen that Penrite has brought out a Everyday 10w40 Full Synthetic. Its $20 cheaper than HPR5. Cant wait to give it a go.

Fark, Just spent $40 something dollars a bottle on HPR5. When's this new stuff released?

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